I no longer use Twitter, so I’m not sure whether this is a possibility now, but it was at one point.
Was the link itself a forwarding link through a potentially spammy/tracking service, even though the end link is a legitimate NPR page? I do not know if Twitter shows the resulting link at the end of a redirect chain in that widget or just what is posted.
I’m also unsure if NPR has any sort of advertising that could be using shady forwarding from the page that Twitter may be seeing in the link. Advertising networks incorporating shady shit on regular pages happens a lot since they don’t actually verify every ad.
Now, I doubt either of those are the case, but they’re possibilities to verify first before jumping on a bandwagon. Twitter is such dogshit now that I doubt they’re doing more than the basic anymore, almost definitely not actually following links and redirects to check for even basic safety stuff like that since Elon took over.